Hoist for loading and unloading objects on a truck bed

ABSTRACT

A hoist for elevating cargo onto the bed of a truck includes a frame which may be mounted to the truck bed, a platform or container which is connected to the frame by a pivoting arm, and an arrangement of linkages for rotating the arm to position the platform either on the truck bed or on a loading and unloading position resting on the ground behind the truck. A threaded screw and an arm tube are connected to the arm via the linkages, with the linkages being arranged to increase the effective “flow” of the arm to provide a long travel distance of the arm. Rotational movement is imparted to the screw by electric, pneumatic and hydraulic systems to extend or retract the cantilever arm as desired.

CROSS REFERENCE TO RELATED APPLICATION

This Continuation-in-Part application claims the benefit of U.S. patent application Ser. No. 10/477,805, filed, Nov. 14, 2003, a National application claiming the benefit of PCT/CA02/00685, having a priority date of May 14, 2001.

FIELD OF THE INVENTION

This invention relates to hoists and more particularly to a hoist for elevating a load-bearing platform from the ground to an open bed of a pickup truck and for returning the platform to the ground using a screw driven by pneumatic or hydraulic or electric systems, each system operated directly from the battery of the pick up truck.

BACKGROUND OF THE INVENTION

Pickup trucks and other vehicles having a cargo-carrying bed are commonly used to transport loads which are too heavy to be manually hoisted, for example, a user might wish to load a small and light vehicle such as a snowmobile, all terrain vehicles (“A.T.V.”) or riding lawn mowers. Such loads are usually loaded onto the truck by pushing or driving them up a ramp and onto the open bed of the truck. Loading of the truck bed in this manner can result in damage to the vehicles or other objects being loaded and injury to persons loading them. An example is the case of loading a vehicle onto a truck bed, using a ramp. The upper edge of the ramp must typically rest solidly on the rear bumper of the truck while the vehicle is being driven up the ramp. If the upper edge overhangs the bumper somewhat, the ramp will become unstable when the weight of the front wheels of the vehicle being loaded is on the overhang. At this point, the ramp will rock and become unstable and the driver may lose control of the vehicle.

On the other hand, if the upper edge of the ramp overhangs the bumper insufficiently, vibration of the vehicle on the ramp may cause the upper edge to fall off the bumper with resulting damage to the vehicle and Injury to the driver.

Similarly, a heavy load such as a large hay bale is manually loaded onto a truck bed only with great difficulty.

It is known to provide a hoist to assist in the loading or unloading of a truck, consisting generally of a cargo-carrying platform or container for resting on a truck bed and a arm for moving the platform between its travelling position on the truck bed and a loading position where it rests on the ground directly behind the truck. Thus, a heavy load can be readily pushed or driven onto the platform while the platform Is resting flat on the ground. The load is then secured and the platform hoisted onto the truck bed. An actuator such as a hydraulic ram, linked to a arm, moves a platform between the travel position supported on the truck bed and loading/unloading position resting on the ground. For example, U.S. Pat. No. 4,175,904 to Airaksinen discloses a container and associated hoist mechanism, whereby the container is moved by a arm between a position on a truck bed and resting on the ground directly behind a truck bed, with the hoist arranged for moving the container between the two positions. Similar arrangements are disclosed in U.S. Pat. No. 5,601,393 to Waldschmitt and U.S. Pat. No. 6,152,674 to Ogrodnick.

It is desirable to provide a hoist, including an associated container or platform, suitable for use with a relatively light vehicle such as a light truck or pickup truck, which is also capable of bearing and hoisting a relatively heavy load such as a pair of snowmobiles.

SUMMARY OF THE INVENTION

The present invention relates to an improved hoist which includes a moveable load-bearing platform which is moveable between a pickup truck bed and a position resting at ground level, and further to a linkage arrangement for moving the platform.

I have invented an improved hoist that will elevate a platform from the ground to an open bed of a pickup truck. A vehicle such as a snowmobile, an A.T.V. and a riding mower can be driven onto the platform while the platform is resting solidly on the ground. The driver can then get off the vehicle and the platform. The hoist will then safely elevate the platform, bearing the vehicle resting on the platform and place these onto the open bed of the pickup truck. The vehicle is then in position to be transported on the pickup truck. Reversing the action of the hoist allows the vehicle to be unloaded from the pickup truck.

The hoist can be bolted into the bed of a pickup truck, can be operated without invading the bed of the pickup truck or requiring holes in the bed of the pickup truck other than the bolt securing holes, and the hoist can be easily removed, freeing the pickup truck for other tasks.

Briefly the hoist of my invention includes a moveable load-bearing platform, a framework adapted to be mounted on the open bed of a truck and having a longitudinally extending stringer; a cantilever arm being dogleg L-shaped and pivotal relative to the stringer and being pivotally interconnected to the platform; and an actuator which is pivotal relative to the stringer and which, when retracting, causes the cantilever to pivot toward the actuator with resulting raising of the platform. The actuator comprises a longitudinally extending member such as a threaded screw, which may be operated by an electric motor driven directly from the truck battery, or pneumatic, or hydraulic devices may also be employed. An arrangement of linkages connects the actuator with the cantilever dogleg L-shaped arm to increase the leverage and “reach” of the actuator thereby permitting the actuator to be relatively short in comparison with the travel distance required of the cantilever dogleg L-shaped arm. For example, it is desirable to provide a sufficient movement of the cantilever dogleg L-shaped arm to lower the platform significantly below the truck wheels. This permits loading of watercraft, or of the platform on an irregular surface. The linkage arrangement comprises a first connecting link member interposed between the actuator and the cantilever dogleg L-shaped arm, this first link member being pivotally joined at a first end to the actuator. The second end of the link member is pivotally engaged to the cantilever dogleg L-shaped arm, at a point close to the pivot mount of the cantilever dogleg L-shaped arm to the stringer. A second, generally upstanding anchoring link is pivotally mounted at its lower end to the stringer, at a point between the actuator and the cantilever dogleg L-shaped arm. At its upper end the upstanding link is pivotally joined to the pivot mount joining the actuator and the first link. The actuator and first link form a scissors-like arrangement which unfolds as the actuator extends, thus increasing the “reach” and lifting force of the actuator. The second link serves to maintain longitudinal rigidity of the link system, i.e. to permit the horizontal thrust of the actuator to be transmitted to the cantilever dogleg L-shaped arm.

In one preferable version, the links are arranged such that they meet at an elbow junction at approximately a 90 degree angle when the actuator and cantilever dogleg L-shaped arm are extended for depositing the platform at ground level. In this position, a retractive force of the actuator may be translated into an upward lifting action of the second link arm acting on the main cantilever dogleg L-shaped arm. The second link arm joins with the cantilever dogleg L-shaped arm at an angle of between 45 and 90 degrees when in this extended position, thereby enhancing the upward lifting and inertial action of the actuator. This shallow angle is desirable to permit the first link to transfer the weight of the cantilever dogleg L-shaped arm against the frame when the actuator retracts or extends.

In another version the actuator is a threaded screw and an arm tube threadably supported on the screw.

Preferably, the platform includes a at least one roller or wheel mounted at its distal end, to facilitate fore and aft movement of platform as the same as loaded and unloaded. A further desirable feature is fore and aft upstanding members at the respective fore and aft ends of the frame, for elevating and supporting the platform above the truck bed, thus permitting space between the truck bed and the platform for the various linkages and actuator. The rearward (aft) member desirably includes one or more rollers to ease the sliding of the platform over the rearward supporting member.

Directional references such as “horizontal” and “vertical” are used for convenience of description. It will be understood that such references are used in relation to the device on a substantially horizontally-disposed truck, and that such terms also include a reasonable and mechanically effective range of angles or positions.

Expressions herein such as “substantially” or “approximately” in reference to dimensions and angles of the invention, cover a range of plus or minus 20% of any expressed length or 15 degrees from any expressed angle.

DESCRIPTION OF THE DRAWINGS

The hoist of the invention is described with reference to the accompanying drawings and photographs. In the drawings:

FIG. 1 is an elevation of the hoist in combination with a platform;

FIG. 2 is a plan view of the lower framework of the hoist;

FIG. 3 is an elevation of the hoist and the platform in position to be loaded;

FIG. 4 is an elevation of the hoist and the platform in position to be transported;

FIG. 5 is an elevation of the lower framework from the side;

FIG. 6 is a plan view of a roller illustrated in FIG. 2, In enlarged scale;

FIG. 7 is a perspective view of the hoist position of the device, with the platform not shown, mounted to the bed of a pickup truck;

FIG. 8 is a perspective view of the device mounted in a bed of a pickup truck, showing in particular the platform portion;

FIG. 9 is a plan view of a second embodiment of the hoist FIG. 10 is a perspective view of the screw device as it would be mounted in a bed of a pickup truck, not show, powered by an electric motor;

FIGS. 11A-C show a perspective, side, and bottom view, respectively, of the screw, screw arm, screw coupler, gear box, and the electric motor in operative position;

FIG. 12 is a schematic view of the components and their wiring connections;

FIG. 13 is a perspective view of the screw device as it would be mounted powered by a pneumatic motor;

FIGS. 14 a-c show a perspective, side, and bottom view, respectively, of the screw, screw arm, screw coupler pneumatic motor, motor mount, and electric pneumatic pump in operative position;

FIG. 15 is a schematic view of the electrical components and the pneumatic drive components;

FIG. 16 is a perspective view of the screw as it would be mounted powered by a hydraulic motor;

FIGS. 17 a-c show perspective, side, and bottom views, respectively, of the screw, screw arm, screw coupler, hydraulic motor, electric hydraulic pump and motor mount in operative position; and,

FIG. 18 is a schematic view of the electrical and hydraulic drive components.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIGS. 1, 2 and 8 the hoist of the invention, generally 10, is shown in conjunction with a platform, generally 12. Hoist 10 has a lower framework 11 which includes a pair of stringers 14, 16, which are fastened to the open bed of a pickup truck 2 and extend longitudinally from the forward wall of the box adjacent to the cab of pickup truck 2 to the rear edge of the bed. Lower framework 11 is sized to conveniently fit within the bed of pickup truck 2. It will be seen that the frame can be scaled up or down in size to permit mounting on a desired size pickup truck 2. The frame is preferably removably mounted by the bed, of pickup truck 2 for example by bolting to the bed of pickup truck 2. The invention is illustrated and described herein in association with a conventional pickup truck 2. It will be understood that any vehicle having a suitable bed will accommodate the invention.

As illustrated in FIGS. 7 and 8, the rear gate of pickup truck 2 is removed to accommodate hoist 10 and platform 12.

A rod 18 extends between stringers 14,16. A cantilever dogleg L-shaped arm 19 is pivotally mounted to rod 18 between stringers 14, 16 at first pivot mount 17. The cantilever is a rigid unitary member comprising of three interconnected segments, an inner segment is 19 a, an intermediate segment 19 b and an outer segment 19 c. The first angle, between intermediate segment 19 b and outer segment 19 c is about 90 degrees while the second angle, between inner segment 19 a and intermediate segment 19 b is about 160 degrees forming the dogleg portion of the L-shaped cantilever arm. While the preferred first angle is about 90 degrees, it is contemplated that a range of angles would be suitable, for example, between 60 degrees and 120 degrees. An angle of substantially 90 degrees is preferable to permit the cantilever to fit snugly against the front wall of platform 12 when platform 12 is in the “travel” position on the bed of pickup truck 2 (e.g. FIG. 4). It will be seen that platform 12 may include a front wall which is canted away from the vertical, and this would lead to a preference that the angle of cantilever arm 19 between intermediate segment 19 b and outer segment 19 c is correspondingly changed. The second angle, between intermediate segment 19 b and inner segment 19 a of the cantilever arm 19, may range between 180 and 140 degrees. The provision of an angle at this position is desirable for permitting the arrangement of linkage, described below, to effectively operate. However, if the first angle is adjusted suitably to other than 90 degrees, it is contemplated that the second angle may be about 180 degrees. Cantilever dogleg L-shaped arm 19 may comprise a rigid metal beam, having a box-like or I-beam cross-sectional configuration. Pivot mount 120 on cantilever arm 19 provides means for attachment of cantilever arm 19 to platform 12.

An actuator 22 is pivotally mounted to stringers 14, 16 adjacent to their forward ends. Actuator 22 may be a hydraulic cylinder 24 and hydraulic ram 26 as disclosed in copending application Ser. No. 10/477,805, or it may be a threaded screw 126 and an arm tube 128, which may be operated by an electric motor 122, or by a pneumatic pump 172, or by hydraulic pump 191. Battery 150 of pickup truck 2 is used to operate these devices. The free end of piston 26 is pivotally connected at pivotal interconnection 39 to first and second links 30, 32. First link 30 is pivotally connected to rod 34 which extends between stringers 14,16. Second link 32 is pivotally connected to cantilever dogleg L-shaped arm 19 at 36.

First link 30 and second link 32 are arranged to increase the lifting power of actuator 22 for rotating cantilever dogleg L-shaped arm 19. In particular, the purpose of first link 30 and second link 32 is to convert a generally horizontal force of actuator 22 into a substantially vertical force for retracting cantilever dogleg L-shaped arm 19, particularly when cantilever arm 19 is in the fully extended position. For this purpose, first link 30 and second link 32 are arranged such that first link 30 is mounted to the frame at a position between actuator 22 and cantilever dogleg L-shaped arm pivot mount 17, and second link 32 is mounted to cantilever arm 19 at a position removed from its pivot mount 17. As will be seen in FIG. 3, when cantilever dogleg L-shaped arm 19 is generally fully extended, first link 30 and second link 32 meet at a substantially right angle at pivotal interconnection 39. First link 30 is about the same length as second link 32, thereby permitting the links to be disposed at about the same angle (i.e. about 45 degrees from the horizontal), when cantilever dogleg L-shaped arm 19 is in the extended position as seen in FIG. 3. This reasonably shallow angle permits first link 30 to transfer a forward thrust in an efficient manner to the frame, when actuator 22 is retracted. This permits first link 30 and second link 32 to provide lift and inertia to cantilever dogleg L-shaped arm 19 as actuator 22 is retracted (and similarly as actuator 22 is extended to lower cantilever dogleg L-shaped arm 19). The linkage arrangement also makes it easier for actuator 22 to be stopped at any position between the extended and retracted positions. It will be seen that a preferred system provides for first link 30 and second link 32, and their respective contact points to be arranged such that second link 32 meets the inner segment 19 a at an angle of between about 350 and 90.degrees from the vertical, when inner dogleg segment 19 a of cantilever arm 19 is horizontal. As suitable arrangement provides an angle of about 45.degree. It will however be seen that the right angle is not critical and first link 30 and second link 32 may meet at a range of angles when inner segment 19 a is horizontal and still serve their desired function. Further, cantilever dogleg L-shaped arm 19 may extend further downwardly from the position shown at FIG. 3, with first link 30 and second link 32 and actuator 22 rotating downwardly in a corresponding fashion. In effect, first link 30 and second link 32 define a folding arm with a pivotal elbow. The elbow is defined by pivotal interconnection 39, with the free end of the piston 26 being pivotally joined to the arm at the elbow joint. Pivotal interconnection 39 may comprise a single pivot connecting the actuator arm and first link 30 and second link 32, or alternatively it may comprise two spaced apart pivots. In one example, the extended actuator length is 477/8 inches, first link 30 has a pivot-to-pivot length of 11.5 inches and second link 32 has a pivot-to-pivot length of 12 inches.

With reference to FIGS. 2, 5 and 6, a first transverse bar 40 extends upwardly from the forward ends of each stringer 14,16 and a second transverse bar 42 extends upwardly from the rear ends of each stringer 14,16. First transverse bar 40 and second transverse bar 42 are mounted to upstanding supports 43. Rollers 44, 46 are mounted at the upper ends of upstanding supports 43. First transverse bar 40 and second transverse bar 42 provide a support for platform 12. Rollers 44, 46 are preferably journalled in a conventional roller bearing mount, on axles 49. Axle mounts 47 support rollers 44, 46 on second transverse bar 42. Rollers 44, 46 have a generally hourglass shape to permit platform rails 61 to “track” on rollers 44, 46 as platform 12 slides on or off the bed of pickup truck 2.

Hoist 10 illustrated in FIGS. 1 through 8 has a single cantilever dogleg L-shaped arm. In a second embodiment, shown at FIG. 9, hoist 90 has two cantilever dogleg L-shaped arms 19 and associated actuators 22 and first links 30 and second links 32 in a paired side-by-side arrangement. The number of cantilever dogleg L-shaped arms is a matter of choice and will depend upon such factors as the proposed maximum loaded weight of the platform, the distribution of the weight and so on.

With reference to FIGS. 3 and 8, platform 12 includes side walls 52, 54, a front wall 56, a rear gate 58 and rollers or wheels 60, 62 which extend from the rear of platform 12. A pair of side rails 59 forms part of lower framework 11 of platform 12. The outer end of cantilever dogleg L-shaped arm 19 is pivotally connected to front wall 56 of platform 12 by way of pivot mount 20. The platform bed may include apertures to receive vehicle wheel blocks to prevent the carried vehicle from rolling. Platform 12 may also include anchors to hold tie-downs to stabilize a load on platform 12. Rear gate 58 swings open about either side or bottom-mounted hinges to permit a vehicle to be driven onto platform 12 or a load to be rolled or slid thereon. Alternatively, rear gate 58 may be lifted out of side brackets 63 for complete removal.

The elevated first transverse bar 40 and second transverse bar 42 to support platform 12, elevated above the linkages and threaded screw 100 of the hoist.

The operation of hoist 10 is as follows: platform 12 is positioned to rest on the ground directly behind pickup truck 2 as seen in FIG. 3. For this purpose, actuator 22 is extended, thereby rotating the cantilever dogleg L-shaped arm 19 into its extended position. The load to be carried by pickup truck 2 is then placed on platform 12. If, for example, the load is a snowmobile or an A.T.V., the vehicle is driven onto platform 12. Rear gate 58 of platform 12 is then closed. The vehicle, or other load, is secured to platform 12 by means of wheel blocks, tie downs or other suitable securing means. Actuator 22 is then activated to retract piston 26. As piston 26 retracts, first link 30 and second link 32 fold together and cantilever dogleg L-shaped arm 19 is rotated forwardly. As actuator 22 is retracted, the thrusting retractive force of piston 26, which is disposed in a near horizontal position, is converted by means of first link 30 and second link 32 into a generally upward retractive force in the manner explained above. The leading edge of platform 12 is drawn forwardly and upwardly, with rails 61 of platform 12 sliding over rollers 44, 46, as illustrated in FIG. 1. The rear edge of platform 12 is supported by wheels 60, 62. When platform 12 reaches the position illustrated in FIG. 1, platform rails 61 contacts rollers 44, 46 and platform 12 then rolls forward in the box of the pickup truck 2, with continued forward movement of platform 12 causing wheels 60 and 62 to leave the ground until platform 12 is fully supported in a generally horizontal position on first transverse bar 40 and second transverse bar 42.

Preferably, a control unit 80 (see FIG. 1) is provided which controls the operation of actuator 22. Control unit 80 includes conventional controls for controlling threaded screw 100, including a remote unit 82 (seen in FIG. 1 as connected by a dotted line to control unit 80) for actuation by a user standing along side or behind pickup truck 2. Control unit 80 may include an emergency shut-off switch which is triggered by e.g. a sudden increase in load indicative of a jam. Remote unit 82 may include a “dead man” switch. Control unit 80 and threaded screw 100 are powered from the electric power supply of pickup truck 2, either by way of a cigarette lighter attachment or a dedicated electrical connection.

When outer segment 19 c of the cantilever dogleg L-shaped arm 19 is vertical as illustrated in FIG. 4, platform 12 will be horizontal and fully supported by first transverse bar 40 and second transverse bar 42. Preferably, platform 12 then will be retained within the confines of the truck bed and not overhang the edges of pickup truck 2.

It will be seen that any suitable vehicle may be used in association with this invention for carrying hoist 10, such as a flat-bed truck, a farm or construction vehicle, a towed vehicle such as a flat-bed trailer, and any other suitable vehicle.

With reference to FIGS. 10,11A-C and 12, hoist 110 has a lower framework 111 which includes a pair of stringers 114, 116, which are fastened to the open bed of a pickup truck 2 (see FIG. 7) and extend longitudinally from the forward wall of the box adjacent to the cab of pickup truck 2 to the rear edge of the bed. Lower framework 111 is sized to conveniently fit within the bed of pickup truck 2.

A rod 118 extends between stringers 114, 116. A cantilever dogleg L-shaped arm 119 is pivotally mounted to rod 118 at its base or bottom end 117 between stringers 114, 116. Cantilever arm 119 is a rigid unitary member comprising of three interconnected segments, an inner segment, the dogleg, is 119 a, an intermediate segment 119 b and an outer segment 119 c. The first angle, between intermediate segment 119 b and outer segment 119 c is about 90 degrees while the second angle, between inner segment 119 a and intermediate segment 119 b is about 160 degrees forming the dogleg portion of L-shaped cantilever arm 119. While the preferred first angle is about 90 degrees, it is contemplated that a range of angles would be suitable, for example, between 60 degrees and 120 degrees. An angle of substantially 90 degrees is preferable to permit the cantilever to fit snugly against the front wall of platform 12 when platform 12 is in the “travel” position on the bed of pickup truck 2 (e.g. FIG. 4). Cantilever dogleg L-shaped arm 119 may comprise a rigid metal beam, having a box-like or I-beam cross-sectional configuration.

Pivot mount 120 on cantilever arm 119 provides means for attachment of cantilever arm 119 to platform 12.

An actuator 22 is pivotally mounted to stringers 114, 116 adjacent to their forward ends by rod 13 extending through pivot mount 121 and stringers 114 and 116. Actuator 22 is a threaded screw 126, which may be operated by an electric motor 122, or by a pneumatic pump 172, or by an electric hydraulic pump 191. Truck battery 150 is used to operate these devices. The free end of screw 126 is pivotally connected at pivotal connection 138 to first link 130. First link 130 is pivotally connected to stringers 114 and 116 at pivotal connection 134. The other end of first link 103 is pivotally connected to second link 132 at pivotal connection 139. First link 30 is pivotally connected to rod 34 which extends between stringers 14,16. Second link 32 is pivotally connected to cantilever dogleg L-shaped arm 19 at 36.

First transverse bar 140 and second transverse 142, which extend across stringers 114 and 116 have supports 143, which support rollers 144 and 146.

As shown in FIGS. 10 through 12, when threaded screw 126 and arm tube 128 are operated by electric motor 122, pivot mount 121 pivotally secures electrically operated screw 126 and arm tube 128 by means of rod 131, which extends through stringer 114 through pivot mount 121 and through stringer 116. Pivot mount 121 is rigidly affixed to gear box 124. Electric motor 122 is operatively connected to gear box 124, which rotates screw coupler 127 and in turn imparts rotation motion to screw 126. Arm tube 128 is threadably attached to screw 126 by arm bushing 129 whereby the rotational motion imparted to screw 126 extends or retracts arm tube 128 along the length of screw 126, thus lengthening and shortening arm tube actuates movement of cantilever dogleg L-shaped arm 119 through its entire motion from fully extended to fully retracted provided the motion necessary to move platform 12 from fully loaded to sitting on the ground (see FIGS. 3 and 4).

First link 130 is rotatably attached at its base end on rod 134, which extends between stringers 114 and 116 and rotatably supports first link 130 therebetween. Second link 132 is pivotally attached along the length of inner segment 119 a of cantilever arm 119. Rod 136 passes through box sides of inner segment 119 a. Second link 132 extends between gusset members 147, which are spaced apart along the inside of the angle formed by inner segment 119A and intermediate segment 119 b of cantilever arm 119. Second end 133 of second link 132 is rotatably attached to first link 130 by pivot 139. Pivot 139 extends between two upper distal ends of first link 130. Second end 125 of arm tube 128 is rotably attached to pivot 138 along the length of first link 130 spaced below pivot 139. Hole 137 in distal end 125 of arm tube 128 to receive pivot 138.

The linkage system is arranged in the form of a tetragon having a base or bottom member made up of a portion of stringers 114 and 116, and having two upright members, first link 130 and the lower portion of dogleg inner segment 119 a of cantilever arm 119, and having an upper member second link 132. These linkage members and the tetragon they form have non-parallel opposing sides which interact to transmit for force exerted by screw 126 and arm tube 128 to dog leg L-shaped cantilever arm 119 to extend or retract the arm to unload or load platform 12 as desired. The tetragon constantly changes shape as cantilever arm 119 moves through its range of motion from fully retracted to fully extended. Threaded screw 126 and arm tube 128 are exterior to the tetragon and extend forwardly therefrom. At their forward end, threaded screw 126 and arm tube 128 are pivotally attached to stringers 114 and 116 by rod 131.

The schematic of the electrical system, shown in FIG. 12, shows battery 150, which is the battery of pickup truck 2, connected through fuse box 151 to junction box 152. Pendant 153 for remote operation of hoist 110 is also attached to junction box 152, as well as limit switches 154 and 155. Limit switch 154 stops motion in the fully retracted position and limit switch 155 is positioned to limit motion in the fully extended position. From junction box 152, electric motor 122 is powered and gear box 124 is driven to impart rotation to screw 126 to extend and retract arm tube 128 as desired as previously described.

As shown in FIGS. 13 through 15, the pneumatic drive system is shown comprising hoist structure 110 as previously described and replacing the electric drive with the pneumatic motor 170, the electric pneumatic pump 172 and air lines 173 and 174, and, motor mount 175, which supports pivot mount 121. Pivot mount 122 allows screw 126 and arm tube 128 to pivot to accommodate the movement of first link 130 and second link 132 and dogleg L-shaped cantilever arm 119 as needed while screw 126 is rotated to extend or retract arm tube 128 as desired.

Electric pneumatic pump 172 is operatively connected to junction box 152, which is otherwise connected as previously described, including battery 150, pendant 153 and fuse box 152, limit switches 154 and 155. Electric pneumatic pump 172 is connected by airlines 173, 174 to pneumatic motor or drive 170.

As shown in FIGS. 16 through 18, hydraulic motor 190 drives electric hydraulic pump 191 with junction box 152 operatively connected therewith as previously described, having hydraulic fluid reservoir 194 operatively connected therewith and hydraulic lines 192 and 193 carrying hydraulic fluid to and from hydraulic drive 190. Hydraulic drive 190 imparts rotation to screw coupler 127 thereby imparting motion to arm tube 128.

It will be understood that modifications can be made in the embodiments of the hoist illustrated and described herein without departing from the scope and purview of the invention. 

1. A pickup truck and a bolt-on removably mounted hoist for loading and unloading objects to said pickup truck bed from the ground level; said hoist comprising: a frame, a platform and a moving structure system; said frame comprising two or more stringers for mounting adjacent to and overlying said pickup truck bed in a generally horizontal orientation when mounted and defining a substantially horizontal plane; said platform being suitable for carrying an object, said platform being displaceable between a first position supported on said pickup truck bed and a second position rearwardly and downwardly displaced from said pickup truck bed; said moving structure system comprises a rigid dogleg L-shaped cantilever arm, a threaded screw, and a linkage system; said rigid dogleg L-shaped cantilever arm for moving said platform between said first and second positions having a first end pivotally mounted to said platform adjacent said upper first end of said platform and having a second ends end pivotally mounted to a rod extending between two said stringers at a point where said cantilever arm will not engage said pickup truck bed as said arm moves through a range of motion; said cantilever arm having a 90 degree bend spaced from said first end thereof so that when said platform is in said first position, said cantilever arm extends generally vertically from said pivotal connection to said platform to a point below said platform and above said stringers where said cantilever arm extends generally horizontally below said platform; said cantilever arm has a second bend spaced from said second end to position said second end of said cantilever arm at said pivotal attachment on said stringers; said threaded screw having first and second ends, said threaded screw being threadably engaged to an arm tube; said first end being pivotally mounted to a forward region of said frame, said second end indirectly connected to said cantilever arm for rotating said cantilever arm; said threaded screw and said arm tube are longitudinally extendable and retractable by imparting rotation to said screw; said linkage system for indirectly connecting said second end of said threaded screws and said arm tube to said cantilever arm; said linkage system comprising first and second elongate rigid links; a first pivot mount joining together said first and second links about a single axis of rotation; second and third pivot mounts joining said first and second elongate rigid links to said stringers and said cantilever arm respectively, wherein said first and second links, a portion of said cantilever arm and said horizontal plane of said stringers respectively define four sides of a tetragon all four sides of which are pivotal relative to each other; said threaded screw and said arm tube being positioned generally forward of said rigid links when folded; said first link being pivotally mounted to said stringers between said threaded screw and said arm tube and said cantilever arm for rotating between a rearwardly leaning position when said threaded screw and said arm tube are fully extended; an intermediate vertical position and a forwardly leaning position when said threaded screw and said arm tube are fully retracted; said first link and said second link indirectly join the second end of said threaded screw and said arm tube and said cantilever arm for transmitting force therebetween; said first link being positioned and configured such that in said rearwardly leaning position the angle between said first and second links is about 90 degrees wherein extension and retraction of said screw and said arm tube actuates said linkage system and said cantilever arm to move said platform between said first and second positions.
 2. The pickup truck and said bolt-on removably mounted hoist as defined in claim 1 wherein opposing sides of said tetragon are non-parallel.
 3. The pickup truck and said bolt-on removably mounted hoist as defined in claim 1 wherein said threaded screw and said arm tube are exterior to said tetragon and extends forwardly therefrom.
 4. The pickup truck and said bolt-on removably mounted hoist as defined in claim 1 having two or more extendible screws and arm tubes, each operatively attached to said cantilever arm and said linkage system.
 5. The pickup truck and said bolt-on removably mounted hoist as defined in claim 1 further comprising an electric motor driving a gear box and a screw coupler to impart rotation to said threaded screw to extend or retract said cantilever arm as desired.
 6. The pickup truck and said bolt-on removably mounted hoist as defined in claim 1 further comprising an electric pneumatic pump driving a pneumatic drive through operatively connected air lines to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired.
 7. The pickup truck and said bolt-on removably mounted hoist as defined in claim 1 further comprising an electric hydraulic pump which moves hydraulic fluid to and from a reservoir and a hydraulic drive to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired.
 8. The pickup truck and said bolt-on removably mounted hoist as defined in claim 1 having two or more extendible screw and arm tubes, each operatively attached to said cantilever arm and said linkage system.
 9. A bolt-on hoist sized to operatively fit in the bed of a standard pickup truck for loading and unloading objects to and from said pickup truck bed and to and from positions at and significantly lower than ground level; said hoist unit comprising: a frame, a moving structure system attached to said frame, and a platform movable by said moving structure system; said frame comprising at least two stringers for mounting adjacent to and overlying said pickup truck bed and presenting a generally flat surface to said pickup truck bed when mounted and defining a substantially horizontal plane; said frame is removably secured to said pickup truck bed by at least two bolts; said platform being suitable for carrying one or more objects; said platform being displaceable between a first position supported on said pickup truck bed and a second position rearwardly and downwardly displaced from said pickup truck bed; said moving structure comprising a rigid dogleg L-shaped cantilever arm, a threaded screw and arm tube, and a linkage system powered from an electric power supply from said pickup truck; said rigid dogleg L-shaped cantilever arm moves said platform between said first and second positions and has a first end pivotally mounted to said platform adjacent said upper first end of said platform and has a second end pivotally mounted to a rod extending between two said stringers at a point where said cantilever arm will not engage said pickup truck bed as said cantilever arm moves from said first position to said second position through a range of motion; said single longitudinally extendible screw and arm tube having first and second ends; said first end being pivotally mounted to a forward region of said frame; said second end indirectly connected to said cantilever arm for rotating said cantilever arm; said cantilever arm having an approximately 90 degree bend spaced from said first end thereof so that when said platform is in said first position, said cantilever arm extends generally vertically from said pivotal connection to said platform to a point below said platform and above said stringers where said cantilever arm extends generally horizontally below said platform; said cantilever arm has a second bend spaced from said second end of said cantilever arm to said position of said second end of said cantilever arm at said pivotal attachment at said stringers; a linkage system for indirectly connecting said second end of said screw and arm tube to said cantilever arm; said screw and arm tube being positioned generally forward of said rigid links when folded; said first link being pivotally mounted to said stringers between said screw and arm tube and said cantilever arm for rotating between a rearwardly leaning position when said screw and arm tube is fully extended, an intermediate vertical position and a forwardly leaning position when said screw and arm tube is fully retracted, and said second link directly joining the second end of said screw and arm tube and said cantilever arm for transmitting force therebetween, said first link being positioned and configured such that in said rearwardly leaning position the angle between said first and second links is about 90 degrees; and, said extension and retraction of said screw and arm tube actuates said linkage system and said cantilever arm to move said platform between said first and second positions.
 10. The pickup truck and said bolt-on removably mounted hoist as defined in claim 9 further comprising an electric motor driving a bear box and a screw coupler to impart rotation to said threaded screw to extend or retract said cantilever arm as desired.
 11. The pickup truck and said bolt-on removably mounted hoist as defined in claim 9 further comprising an electric pneumatic pump driving a pneumatic drive through operatively connected air lines to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired.
 12. The pickup truck and said bolt-on removably mounted hoist as defined in claim 9 further comprising an electric hydraulic pump which moves hydraulic fluid to and from a reservoir and a hydraulic drive to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired.
 13. The pickup truck and said bolt-on removably mounted hoist as defined in claim 9 having two or more extendible screws and arm tubes, each operatively attached to said cantilever arm and said linkage system.
 14. The pickup truck and said bolt-on removably mounted hoist as defined in claim 9 having two or more extendible screws and arm tubes, each operatively attached to said cantilever arm and said linkage system.
 15. A pickup truck and a bolt-on removably mounted hoist for loading and unloading objects on the bed of a vehicle, said hoist comprising: a framework for mounting on said bed of said vehicle; said framework including a longitudinally extending stringer; a platform for receiving an object from loading onto said bed of said vehicle; said platform being moveable between a first position supported on said bed of said vehicle and a second horizontal position rearwardly displaced from said bed to receive an object thereon; a cantilever arm for moving said platform and having a first end and a second end; said first end being pivotally jointed to said platform and said second end being pivotally joined to said stringer at a point where said cantilever arm will not engage said bed of said vehicle as said cantilever arm moves through a range of motion; said cantilever arm having a 90 degree bend spaced from said first end thereof so that when said platform is in said first position, said cantilever arm extends generally vertically from said pivotal connection to said platform to a point below said platform and above said stringers where said cantilever arm extends generally horizontally below said platform; said cantilever arm has a second bend spaced from said second end to position said second end of said cantilever arm at said pivotal attachment on said stringers; a longitudinally extendable actuator comprising a threaded screw and a threadably engaged arm tube; said actuator having a first end and a second end; said first end being pivotally mounted to said framework at a forward region thereof; a linkage arrangement joining said second end of said actuator to said cantilever arm for rotating said cantilever arm for selectively raising and lowering of said platform; said linkage arrangement comprising a first generally upstanding pivotal link connecting said second end of said actuator with said framework; a second pivotal link connecting said second end of said actuator with said cantilever arm; and, said pivotal links both being pivotally mounted at both ends thereof.
 16. The pickup truck and said bolt-on removably mounted hoist as defined in claim 15 further comprising an electric motor driving a gear box and a screw coupler to impart rotation to said threaded screw to extend or retract said cantilever arm as desired.
 17. The pickup truck and said bolt-on removably mounted hoist as defined in claim 15 further comprising an electric pneumatic pump driving a pneumatic drive through operatively connected air lines to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired.
 18. The pickup truck and said bolt-on removably mounted hoist as defined in claim 15 further comprising an electric hydraulic pump which moves hydraulic fluid to and from a reservoir and a hydraulic drive to impart rotation to a screw coupler and said screw to extend or retract said cantilever arm as desired.
 19. The pickup truck and said bolt-on removably mounted hoist as defined in claim 15 wherein said linkage arrangement forms a tetragon; and, said tetragon having non-parallel opposing sides.
 20. The pickup truck and said bolt-on removably mounted hoist as defined in claim 15 wherein said linkage arrangement forms a tetragon and said threaded screw and said arm tube are exterior to said tetragon and extend forwardly therefrom. 